通过实验我们发现蚯蚓更喜欢（　　）的泥土。

在平面直角坐标系 $xOy$ 中，圆 $C_1$ 的参数方程为 $\text{{}\begin{array}{c}x=-1+acos\theta ,\\ y=-1+asin\theta ,\end{array}$ （ $\theta$ 为参数， $a$ 是大于0的常数）．以坐标原点为极点， $x$ 轴正半轴为极轴建立极坐标系，圆 $C_2$ 的极坐标方程为 $\rho =2\sqrt{2}\text{cos}\left(\theta -\frac{\pi }{4}\right)$ ．

小伟能自己乘公交车上学，我们应该向他学习。（    ）

增加：在缺词处加一个漏字符号（∧），并在此符号下面写出该加的词。

删除：把多余的词用斜线（＼）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1).每处错误及其修改均仅限一词；

2).只允许修改10处，多者（从第11处起）不计分。

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